Add docker-compose file for tests

README.md

 ## Tests [![CircleCI](https://circleci.com/gh/csmith/docker-service-reporter-lib.svg?style=svg)](https://circleci.com/gh/csmith/docker-service-reporter-lib)
 
 A separate Dockerfile for tests is located in the tests directory. It depends
-on a 'dev' label of csmith/service-reporter-lib. You can build and run the
-tests like so:
+on a 'dev' label of csmith/service-reporter-lib. There's a docker compose file
+to build them together:
 
 ```
-docker build -t csmith/service-reporter-lib:dev .
-docker build -t csmith/service-reporter-lib-test:dev test
-docker run --rm -it csmith/service-reporter-lib-test:dev
+cd test
+docker-compose build
+docker-compose run tests
 ```
 

circle.yml

     - docker
 
 dependencies:
+  pre:
+    - pip install docker-compose
   override:
-    - docker info
-    - docker build -t csmith/service-reporter-lib:dev .
-    - docker build -t csmith/service-reporter-lib-test:dev test
+    - docker-compose build
+  pwd: test
 
 test:
   override:
-    - docker run -it csmith/service-reporter-lib-test:dev
+    - docker-compose run tests
+  pwd: test
 

test/docker-compose.yml

+---
+version: '2'
+
+services:
+  reporter:
+    build: ..
+    image: csmith/service-reporter-lib:dev
+    networks: ['testing']
+  tests:
+    build: .
+    image: csmith/service-reporter-lib-test:dev
+    depends_on: ['reporter']
+    networks: ['testing']
+
+networks:
+  testing:
+